Mutants which activate or block various components of flight behavior in Drosophila melanogaster will be used to investigate the organization of these components and their underlying neuronal mechanisms. More specifically, these mutants will be used to generate mosaic flies. These composite individuals, each consisting of mutant and normal tissue, will be used to determine which part of the nervous system must be mutant in order that the mutant behavior be expressed. The mosaic results will be correlated with neuroanatomical and electrophysiological data from normal, mutant, and mosaic flies.